Carbonyl-dianion

The combination of carbonylate dianions with silicon tetrachloride leads in high yields to the p-Si compounds 22-24. As already mentioned, the reaction can be performed either stepwise with isolation of the dichlorosilylene complex or in a one-pot procedure. The resulting products show a surprisingly high thermal... 

Reactions Beginning with Trivalent Group 13 Element Halides with Metal Carbonyl Dianions... 

In the reaction of group 13 element halides with metal carbonyl dianions, the analysis is more complex than observed for the reactions with metal monoanions. Upon addition of metal dianions to EX3 or REX3, either one or two halide ions may be eliminated. When only one halide ion is eliminated per added metal dianion, the complexes may still be viewed as E3+ derivatives (Equations (33)-(36)).19 This may be controlled to some extent by the stoichiometry of the reaction. Comparison of Equations (33)19 and (34)19 shows that the electron demand at the main group element can be satisfied by coordination either to an electron-rich metal center 26 or formation of a halide bridge 27. Ligand-stabilized forms may also be prepared in this fashion (Equation (36)).19... 

The phase-transfer catalysed reaction of nickel tetracarbonyl with sodium hydroxide under carbon monoxide produces the nickel carbonyl dianions, Ni,(CO) 2- and Ni6(CO)162, which convert allyl chloride into a mixture of but-3-enoic and but-2-enoic acids [18]. However, in view of the high toxicity of the volatile nickel tetracarbonyl, the use of the nickel cyanide as a precursor for the carbonyl complexes is preferred. Pretreatment of the cyanide with carbon monoxide under basic conditions is thought to produce the tricarbonylnickel cyanide anion [19], as the active metal catalyst. Reaction with allyl halides, in a manner analogous to that outlined for the preparation of the arylacetic acids, produces the butenoic acids (Table 8.7). 

X-ray diffraction studies on salts of the nickel and platinum carbonyl dianions [M3(CO)3(m2-CO)3] 2 (M = Ni, Pt) showed that these... 

There have been several recent reports of the reduction of carbon dioxide to carbon monoxide by transition metal complexes. Maher and Cooper (2/) have reported that several metal carbonyl dianions can effect the disproportionation of C02 to metal bound carbon monoxide [Eq. (37)] with Li2C03... 

Ito, Y. Matsuura, T. Murakami, M. N-Substituted organo(silyliminomethyl)stannanes synthetic equivalent to organosilyl carbonyl anion and carbonyl dianion. J. Am. Chem. Soc. 1987, 109, 7888-7890. 

Cluster Compounds.—An interesting new series of platinum carbonyl dianions of formula [Pt3(CO)3(p2-CO)3]2 n = 2—5) have been synthesized by reduction of [PtClg]2" with CO and methanolic NaOH.107 Species with decreasing n were isolated with increasing concentration of reducing agent (equation 18). The X-ray... 

Carbonylation by the S l mechanism of 2-methyl-2-dodecyl chloride and bromide by the carbonyl dianion Na2Fe(CO)4 has been also reported127. 

J. C. Calabrese, L. F. Dahl, A. Cavalieri, P. Chini, G. Longoni, and S. Martinengo, Synthesis and Structure of a Hexanuclear Nickel Carbonyl Dianion, [Ni3(CO)3( j,2-CO)3]22, and Comparison with the [Pt3(CO)3(p2-CO)3]22 Dianion. An Unprecedented Case of a Metal Cluster System Possessing Different Metal Architectures for Congener Transition Metals, J. Am. Chem. Soc. 96, 2616-2618 (1974). 

Consequently the corresponding silylene transition metal complexes with coordination number three at silicon are accessible. In contrast the reaction of dichlorosilanes with carbonylate dianions in the presence of a donor solvent yields donor stabilized silylene complexes (coordination number at silicon 3+1). 

One of the broadest and historically most important areas of dimetal chemistry is that of the simple carbonyl complexes (see Carbonyl Complexes of the Transition Metals). As mentioned above, Co2(CO)s, Fe2(CO)9, and Mn2(CO)io were among the first metal-metal bonded complexes characterized. To this day, these complexes continue to be involved in new chemistry, for example, Co2(CO)g found recent use in a one-pot synthesis of tricyclic 5-lactones .In the case of molybdenum, the zerovalent carbonyl is monomeric however, reduction gives a dinuclear metal carbonyl dianion in which the metal is in the [-1] oxidation state (equation 6). 

An important class of metal-metal bonded dimers is the hydrido-bridged carbonyls (see Hydrides Solid State Transition Metal Complexes). These can be obtained through a number of reactions, most commonly, through protonation and direct reaction with hydrogen. Protonation of the metal carbonyl dianion Mo2(CO)io yields the complex shown in equation (10). 

Reactions with carbonylate dianions, for example, [W(CO)s], [Fe2(CO)g], and others, also produce a rich cluster chemistry. Ligands other than CO can be included in the carbonylate anions, for example, NO, PR3, SR, SCN, NCO, and CN increasing the scope of cluster derivatization of these synthetic procedures as in (179). ... 

Formaldehyde dithioacetals are often utilized as synthetic equivalents of formyl anion ( CHO) and carbonyl dianion ( "C=0). 1,3-Dithiane is commonly used its 2-H is quite acidic (pKt = 31.1) due to sta-... 

Inserting just a methylene unit is not particularly exciting from a synthetic point of view. It is much more interesting to consider functionalized eonjune-tive reagents. An important synthon of this sort is the carbonyl-dianion. Of the reagents corresponding to this synthon, dithiane is used most frequently [113] (Scheme 2.62). 

---